New York, Aug 11 (IANS): Increased levels of a molecule in the brain, called hypocretin, may contribute to cocaine addiction, new research has found.

"Cocaine addiction is a disorder that affects millions of people worldwide," said co-author of the study Marisa Roberto, Professor at The Scripps Research Institute (TSRI) in La Jolla, California.

"Understanding the mechanisms underlying cocaine addiction is important for identifying potential new targets for therapeutic use," Roberto noted.

The findings, published in the journal Biological Psychiatry, suggest that blocking hypocretin may reduce compulsive drug-seeking behaviour.

"The results of this study would suggest that the hypocretin system could be considered a pharmacological target, with the hopes that such a medication could be used in combination with cognitive behavioural therapies," co-author Brooke Schmeichel from National Institute on Drug Abuse in the US said.

In the new study, the researchers, led by Schmeichel, focused on changes in the central amygdala, a brain region associated with stress and negative emotions during drug withdrawal.

For the study, one group of rats was given the option to self-administer cocaine for one hour a day, mimicking conditions of short-term, occasional drug use.

A second group had the option to self-administer cocaine for six hours a day, which mimicked the conditions that lead to compulsive drug use and addiction.

The researchers found that compulsive cocaine use triggers a dangerous cycle in the brain, with cocaine sensitising the brain's hypothalamic hypocretin/orexin (HCRT) system, which motivates further drug-seeking.

Hypocretin is a main player in the brain's HCRT system.

Specifically, compulsive cocaine use leads to increased hypocretin, which contributes to overactivity in the central amygdala.

This overactivity corresponds with an anxiety-like state in rat models that appears to help maintain the motivation to continue to seek the drug, the study said.

"The rats escalate their daily intake as many human users would," Roberto said.